RESUMEN
We report the results on infrared transmission measurements of non-doped and tellurium-doped crystals of zinc selenide grown from the melt. It was found that non-doped samples feature high transmission (50%-60%) for the wavelengths of 1-22 µm. The efficient scintillating crystals of ZnSe(Te) are almost opaque for λ>7 µm. Doping these samples with ytterbium from the gas phase does not achieve any significant transmission increase for non-doped ZnSe samples in the spectral range of 1-22 µm. However, it considerably increases (up to 50%) transmission for doped ZnSe(Te) at the wavelengths λ>10 µm. These optical peculiarities were analyzed taking into account restructurization of point defect ensembles created by Te and Yb impurities.
RESUMEN
We analyze physical models accounting for deep-level conduction band transitions to describe impurity absorption spectra in tetrahedral-structured semiconductors. The investigations were carried out for ZnSe crystals doped with transition metals (Ti, V, Cr, Mn, Fe, Co, Ni) from a vapor phase. It was shown that the impurities provide acceptor centers with ground state energy offset by 0.3-0.6 eV from the edge of the conduction band, forming long-wave bands in the absorption spectra of the materials studied.
RESUMEN
This paper is dedicated to study the thin polycrystalline films of semiconductor chalcogenide materials (CdS, CdSe, and PbS) obtained by ammonia-free chemical bath deposition. The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement. Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials. Both effects are attributed to the material porosity which is a typical feature of chemical bath deposition technique. The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction. Quantum mechanical description of the nanopores in semiconductor is given based on the application of even mirror boundary conditions for the solution of the Schrödinger equation; the results of calculations give a reasonable explanation of the experimental data.
RESUMEN
Cylindrical nanostructures, namely, nanowires and pores, with rectangular and circular cross section are examined using mirror boundary conditions to solve the Schrödinger equation, within the effective mass approximation. The boundary conditions are stated as magnitude equivalence of electron's Ψ function in an arbitrary point inside a three-dimensional quantum well and image point formed by mirror reflection in the walls defining the nanostructure. Thus, two types of boundary conditions - even and odd ones - can be applied, when Ψ functions in a point, and its image, are equated with the same and the opposite signs, correspondingly. In the former case, the Ψ function is non-zero at the boundary, which is the case of a weak confinement. In the latter case, the Ψ function vanishes at the boundary, corresponding to strong quantum confinement. The analytical expressions for energy spectra of electron confined within a nanostructure obtained in the paper show a reasonable agreement with the experimental data without using any fitting parameters.
RESUMEN
We consider a multiferroic chain with a linear magnetoelectric coupling induced by electrostatic screening at the ferroelectric/ferromagnet interface. We study theoretically the dynamic ferroelectric and magnetic response to external magnetic and electric fields by utilizing an approach based on coupled Landau-Khalatnikov and finite-temperature Landau-Lifshitz-Gilbert equations. Additionally, we make comparisons with Monte Carlo calculations. It is demonstrated that for material parameters corresponding to BaTiO(3)/Fe the polarization and the magnetization are controllable by external magnetic and electric fields, respectively.
RESUMEN
The approach based on kinetic equations is used to describe spin polarization of conduction electrons in a semiconductor doped with d or f atoms and subject to circularly polarized radiation. In the stationary state we find analytical expressions for the spin polarization of band electrons, ρ(e), and spin polarization of electrons in the impurity levels, ρ(i). It is shown that the degree of spin polarization of the band electrons is mainly determined by the polarization type of the light. On the basis of numerical results we conclude that ρ(e) and ρ(i) are practically independent of the long-term relaxation processes in the subsystem of magnetic impurities.
